Fluorosilicone rubbers have excellent heat resistance, low-temperature resistance, chemical resistance, and other properties and are used in various fields. However, since fluorosilicone rubbers have poor bondability to metals, plastics, and the like, their uses in composite structures with these materials have been limited.
In order to overcome the above problem, it has been proposed to subject the surfaces of metals, plastics, and the like to primer treatment so as to a strongly bond fluorosilicone rubbers to these materials or to form fluorosilicone rubber coatings strongly adhering to those materials. For this purpose, various primer compositions have so far been proposed.
Known primer compositions of this kind include those disclosed in JP-B-53-14580 and JP-A-59-182865. (The terms "JP-B" and "JP-A" as used herein mean an "examined Japanese patent publication" and an "unexamined published Japanese patent application", respectively.) These primer compositions, however, are defective in that for obtaining sufficient adhesion-improving effects with these primer compositions, the fluorosilicone rubber should be heat-pressed to adherends for a long period of time at high temperature and pressure, because they are almost ineffective when used in hot-air vulcanization bonding under ordinary pressure. Further, the bonding of fluorosilicone rubbers to plastics such as nylon and polyethylene terephthalate cannot be sufficiently improved by the above-proposed primer compositions.